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API select

Used to traverse a list. This function is usually used to capture the arguments passed to an ellipsis (...). The official usage of this function is to return a list (retN) starting from index to the end of the list (list).

local ret1, ret2, retN = select(index, list) 

Arguments

Parameters

index 
Any non-zero number or the string "#".
list 
Usually an ellipsis (...).

Returns

retN 
The number of items in the list or every value starting from index to the end of the list.

Examples

-- Common usage. local num = select('#', ...) -- Returns the number of arguments in the ellipsis. local arg = select(i, ...) -- Returns the value at index i. 
-- Print all of the function's arguments (those passed to the ellipsis (...) only) to the default chat frame. local msg for i = 1, select('#', ...) do     msg = select(i, ...)     DEFAULT_CHAT_FRAME:AddMessage(msg) end 
local a, b, c = select(2, 'a', 'b', 'c') -- a = 'b' -- b = 'c' -- c = nil 

Catenation

select can be used to catenate a vararg list into an array. This is useful for returning info from GetBinding, which returns a vararg list of unknown size.

function MyAddon_Catenate(...)     local t,v     t = {}     for i = 1, select("#", ...) do         v = select(i, ...)         tinsert(t, v)     end     return t end 

Notes

  • An alternative solution is to use a declaration like this:
    local args = {...}
    This has the advantage of being portable to standard Lua (although redundant, since standard Lua would make this assignment implicitly) and more readable to non-WoW Lua programmers.
  • list can be value1, value2, value3, ... valueN; although, you will never see it used in that manner since you can just access value1 through valueN directly.
  • It is not recommended that you use this method on a table as you would have to pass the table to unpack() for every call to select (once plus the number of consecutive numeric indexes). For tables, use pairs() or ipairs().
  • Indexes beyond the number of list items will return nil.
select(6, 'see', 'dog', 'run') -- returns nil
  • An index of 0 will produce an "index out or range" error.
  • Negative values wrap to the end of the list.
select(-1, 1, 2, 3, 4, 5) -- returns 5
  • A decimal index will be rounded to the nearest integer (1.1 rounds to 1, 1.9 rounds to 2).
  • Passing a function that returns a list as a parameter to another function will pass each return as a parameter to the function as if you were manually passing each variable to that function, so tinsert(tab, select(1, ...)), will have unpredictable results.
-- these are identical -- number 1 local msg, r, g, b, a, id = select(1, ...) DEFAULT_CHAT_FRAME:AddMessage(msg, r, g, b, a, id)  -- number 2 DEFAULT_CHAT_FRAME:AddMessage(select(1, ...))
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